1. Field of the Invention:
The present invention relates to a new articulated mechanical joint for use, in particular but not exclusively, in knee braces intended to reinforce an injured knee joint particularly during convalescence or permanently in the case of a weak joint. Such braces are also used by athletes to prevent knee injuries.
2. Brief Description of the Prior Art:
The thigh and leg of the human body are articulated to each other through the knee joint of which the principal motions are extension and flexion by rotation about a horizontal axis extending across the knee in a medial-lateral direction. These motions are complex as they take place about a rotation axis which is not fixed, as in the elbow, but shifts slightly across the knee in an anterior-posterior direction. It is important, for an adequate knee brace, to follow the shifting path of the rotation axis of the knee as closely as possible. Additionally, and particularly in the case of injured or weak knees, means must be provided in the artificial joint of the brace, to control extension of the knee joint and usually stop it short of 15.degree. to 5.degree. of full extension. It is indeed in this range that important knee ligament injuries occur.
Another type of rotation is one that takes place about a further horizontal axis which extends in an anterior-posterior direction, that is tranverse to the plane of extension and flexion. This motion may give rise, in an injured or weak knee, also to severe knee ligament injuries. An appropriate knee brace should consequently protect the knee against sidewise motion about this further horizontal axis, both during extension and flexion motions and this protection should not interfere with the latter motions.
The patent and scientific literature is replete with proposals for knee braces including a mechanical joint pivoting about a single fixed axis or a somewhat movable axis which cannot move parallel to the complex motion of the knee. Nor does any provision available control extension fully adequately and adjustably so that the latter will not exceed a predetermined limit, usually within the 15.degree. to 5.degree. short of full extension, as noted above, where ligament and muscle injuries are mostly experienced. It seems also that while much attention has been given to firmly securing the links to the mechanical joint, pivoted together at one end, to the corresponding thigh and leg, less attention is given to the pivot joint itself coupling the links. The pivot joint however is the main component of the knee brace as it is the one that transmits the full loads between the thigh and the leg. Lack of adequate sturdiness in this pivot joint consequently gives rise to possible dangerous sidewise motions during flexion and extension.